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First Posted: Aug 6, 2008
May 28, 2013

Thrush in Horses

by Debora Johnson

See also my Lameness article
Thrush (Merck Vet Manual)

Most every horse owner has seen thrush at one time or another. You pick up your horse's foot to pick the hoof and you see it and smell it!

What is Thrush?

Thrush is of bacterial origin, fusobacterium necrophorum, that can thrive in the region of the frog, cleft and sole of the hoof. Some horses are more prone to thrush. If the hoof has deep clefts or contracted heels they are more prone to get the infection. That type of conformation traps mud, tends to hold moisture, is not open to the air and provides an environment that makes thrush happy. Thrush is an anaerobic bacteria. That means the bacteria thrives without oxygen. Predisposition or not any horse can get thrush. If left untreated the thrush can get into the sensitive tissues of the hoof and cause great pain. Your horse might present with lameness, react when you pick his hoof, or you might notice an ooze or even blood, along with a nasty odor. Call the vet immediately.

Symptoms

  • Foul Odor
  • Black yuck on underside of hoof
  • Dark stain after removing black substance
  • Horse sensitive when hoof is picked
  • Sometimes lameness
  • Loss of frog shape and integrity

Some Causes

  • "Chronic Heal Pain - As you might expect, horses with pain along the palmar aspect (back) of the foot tend to underload this area. The heels, like all other aspects of the foot, are dynamic in nature and respond to applied forces. This is why chronic underloading of the heels results in their contraction. Contracted and/ or high heels produce deep frog sulci, which provide an exceptional environment within which anaerobic bacteria can proliferate. At The ATLANTA Equine Clinic, our first objective when treating a horse with thrush is to resolve any issue(s) that might predispose the horse to chronic underloading (and contraction) of the heels. In our experience, successful management of these issues (the most common of which is thoracic navicular inflammation) eradicates the thrush (which would be considered secondary to the contracted heels) in more than half of the cases.
  • Lack of Exercise - In our experience, one of the more important factors in avoiding and/or eliminating thrush is exercise. For example, horses living in manure and mud might be working hard each day, getting a lot of activity and moving in a natural manner that promotes good vascularity (blood supply) in the foot, which is key to keeping the hoof healthy. Whereas horses standing in clean/dry stalls are simply standing, and are not promoting the same kind of vascularity necessary to generate a healthy foot.
  • Regular Farriery - The horse that is receiving regular maintenance from a farrier will maintain a more balanced and supportive hoof. Such balance lends itself to even loading, compression, and concussion, all of which promote good vascularity and overall foot health. Impaired blood circulation ranks high on the list of causes of thrush. On average, the circulation in a shod or peripherally loaded hoof is approximately 20% of what it is in a healthy barefoot hoof. Moreover, most shod horses land toe-first or flat. The primary problem in these feet isn't thrush, its impaired circulation and incorrect use of the foot.

    Frog Conformation - Open and calloused, atrophied or over trimmed frogs may be susceptible to development of thrush. Frogs with deep cracks, crevices and flaps are also prone, as they are robbed of their protective horn.

  • Diet High in Carbs - There may be a dietary component as well, as horses on high carbohydrate diets seem more likely to be affected with thrush.
  • Hoof Conformation - Horses may walk on the sides of their feet or favor their toes when they have thrush to avoid 'hoof mechanism', the flexion in the hoof that enables shock absorption. Good blood circulation is necessary for a healthy frog, so good heel-first movement is a priority.
  • Previous Injury - Horses sustaining an injury that results in favoring of one limb over another often end up with a contracted heel on the foot of the affected limb. Contraction can result in the development of crevices that welcome proliferation of anaerobic bacteria.
  • Environmental Dificiencies - Of course wet footing is the primary concern, as it creates and environment amenable to bacterial growth and proliferation.

  • Poor Hygiene - Chronic exposure to urine, which contains ammonia, can dissolve the proteins that comprise the frog's horn."

Treatment

When treating thrush you must be careful because you can get thrush, as well. Always use plastic gloves. Always wash up after treatment with soap and water. I also would use some sort of anti-bacterial on my hands, as well. It is also important to know that thrush can survive in the environment for many months. Other horses in the stable or pasture can contract thrush from an infected horse. There are a number of products that can be purchased over-the-counter. Among them are Thrush Relief Gel, Well-Horse Thrush Treatment, Thrush Buster, Thrush XX, Thrush Remedy, Thrush Antisep Huuf Magic, Thrush XXT, Kopertox, and others. My farrier suggested White Lightning regularly to prevent white line disease. I use it and this does double duty and also prevents thrush. If the thrush gets really bad, pack cotton soaked in the treatment into the affected area. I purchased a horse that had bad thrush and the vet used flagel pounded into a powder and mixed in utter cream. I used that mixture and packed the affected tissues with the soaked cotton. That is a severe remedy for bad thrush, but it did the trick. Sometimes people will suggest bleach. I stay away from bleach because it can burn the tissues and parts around the hoof. There are other home remedies such as sugardine which is made by mixing sugar and betadine or iodine. It is then packed in the clefs of the feet with soaked cotton. Always consult your vet before using these remedies.

  • Consult your vet first
  • Use protective plastic gloves
  • Pick the horse's feet
  • Clean the clefts carefully
  • Use disinfectant and warm water to clean the feet
  • Dry the feet and hooves
  • Apply the product your vet suggests

Prognosis

Thrush should respond to treatment. It takes time to kill it, but the outcome is usually good. Unless the case is severe there generally are not any long term problems.

Prevention

  • Have regular farrier appointments
  • Keep horse's environment dry
  • Keep horse's environment clean
  • Do not let your horse stand in urine or manure
  • Keep horse's bedding clean
  • Pick your horse's feet at least two times a day if possible

Nature's Hoof Barefoot and Balanced/Excellent Images of Thrush
Thwarting Thrush


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